1. Field of the Invention
The present invention relates to an optical fiber lighting apparatus.
2. Description of the Related Art
There has been proposed an optical fiber lighting apparatus that has LEDs arranged at the proximal end portion of an endoscope and guides light to the light-emitting unit at the distal end of the endoscope via an insertion portion by using a fiber bundle. The fiber bundle is a single bundle on the endoscope distal end side but is separated into three parts on the light source side, which are respectively and optically connected to the LEDs that emit red light, green light, and blue light.
This optical fiber lighting apparatus guides illumination light from the endoscope proximal end portion to the endoscope distal end portion by using the fiber bundle. Since the light guide efficiency of an optical fiber generally depends on the wavelength, the RGB output ratio at the incident end and that at the exit end are different depending on the length of the fiber bundle. In order to obtain a desired RGB output ratio at the exit end, the RGB output ratio at the incident end has to be adjusted in accordance with the length of the fiber bundle.